This detected some paper cuts within cli tests for example.
The main goal is to decrease friction when actually deploying indexer related
services (backend, indexers, ...).
The pg backends tests should still be reasonably fast as it's using the
swh.core.db.pytest_plugin (which truncate tables in between tests).
~> a rapid look in the phab diff [1] shows that the overall execution time is
reasonably the same as before.
Related to T2821
[1] https://jenkins.softwareheritage.org/job/DCIDX/job/tests-on-diff/